You can do it with colours. Just knock on the door of your new neighbours and call your old ones over. It may be just what you need to break the ice and build new friendships.
You can do it with food. Just take a platter of sweets and eats to the neighbours you pass in the elevator on and off on your way to work. No one can stay aloof over a plateful of Holi delicacies and it may be the start of a colourful relationship.
There is no better way to bond with your little kids than starting your very own new tradition especially for the family. For instance, make your own colours that will be safe for little ones and all the family.
You can mix any food colour in corn-flour and keep it to dry. Grind it to a powder once dried. This however, will need some planning in advance.